An aqueous solution of a mixture of two inorganic salts, when treated with dilute `HCl`, gave a precipitate `(P)` and a filtrate `(Q)`.The precipitate `P` was found to dissolve in hot water. The filtrate `(Q)` remained unchanged, when treated with `H_(2)S` in a dilute mineral acid medium. However, it gave a precipitate `(R)` with `H_(2)S` in an ammoniaca medium.The precipitate `R` gave a coloured solution `(S)`, when treated with `H_(2)O_(2)` in an aqueous `NaOH` medium. The precipitae `P` containsA. `Pb^(2+)`B. `Hg_(2)^(2+)`C. `Ag^(+)`D. `Hg^(2+)`